Mistletoe, scientifically named Viscum album, is a semi-parasitic plant that lives in or on various tree hosts, from the body of which it obtains nutriment, and as many as about 1,500 species thereof, which belong to about 30 genuses, are now known to be present over the world. Of various mistletoes, the species belonging to the genus Viscum, especially Viscum album loranthacea that inhabits European areas, are used as medicinal materials. From a long time ago, such European loranthacea mistletoe had been used as a mysterious folk remedy curative of hypertension, arteriosclerosis, cancers, etc. In 1921, the loranthacea mistletoe was acknowledged to be of anticancer activity nd, from then, has been used as a curative or a therapeutical aid against tumors.
Accordingly, active research has been directed mainly to the biological activity of the European mistletoes, reporting that they have the immunity enhancement effect of stimulating humoral and cell-mediated immune systems as well as activate macrophages and natural killer cells, both taking direct and indirect part in controlling tumor cells, to inhibit the growth of tumor cells and improve the viability of patients suffering from cancers. Also, mistletoe is found to exert cytotoxicity directly on tumor cells. Representative of active materials of mistletoe are lectin components, which are divided into letin-I, -II and III according to sugar chain specificity and molecular weight. Immunological and biochemical attention is being paid largely to lectin-I.
Korean mistletoe (viscum album coloratum), distinguishable from European mistletoe, has been used as medicinal materials effective for the treatment of lumbago, hypertension and teethache and the prevention of miscarriage in Korean folk remedies and Oriental herb medicine. Particularly, in Oriental herb medicine, different names are given to mistletoes in accordance with the kinds of the host trees, suggesting that there might be differences in medicinal efficacy and effective component between the mistletoes which grow in or on different host trees. As a matter of fact, European mistletoes were reported to be different from one to another in lectin components in accordance with their host trees. Hence, the possibility cannot exclude that Korean mistletoes might be also different in components on account of their different host trees.
On the basis of such possibility, Khwaja et al. reported the anti-tumor effects and active components of Korean mistletoes for the first time in Korea, asserting that, unlike European mistletoes, the anti-tumor effects of Korean mistletoes come from the cytotoxicity attributable to alkaloids of strong toxicity rather than from lectins and thus, Korean mistletoes are quite different from European ones in active components against tumors and anti-tumor activity mechanism. However, no details for the difference have yet been reported.
Recent research of the present inventors has demonstrated that Korean mistletoes also directly activated macrophages to induce the secretion of interleukin-1 (hereinafter referred to as “IL-1”)and tumor necrosis factor-α (hereinafter referred to as “TNF-α”) and that the activators to induce the secretion of these cytokines are proteinaceous ingredients which are precipitated by mmonium sulphate. In result, two kinds of lectins were isolated from Korean mistletoes.